The present invention relates to a method of machining optical components such as surface generating with the use of a machining tool such as grinding wheel, more particularly, a method of machining optical components by a grinding with electrolytic inprocess dressing, and an apparatus for carrying out such a method.
The grinding with electrolytic inprocess dressing for performing surface machining with the use of grinding wheel is well known. For example, such a grinding is disclosed in Transactions of the Japan Society of Precision Engineering, Autumn, 1988, and Transactions of the Japan Society of Precision Engineering, Spring, 1989.
Such a grinding method disclosed in the above articles are explained in FIGS. 14a and 14b.
FIG. 14a shows a principle of grinding with electrolytic inprocess dressing and FIG. 14b is a right side view showing a part of FIG. 14b.
As shown in FIG. 14a, the grinding with electrolytic inprocess dressing comprises an electrolytic dressing power supply source 230, a lead wire 236 connected to an anode electrode (+) of the supply source 230, a supplying brush 231 and a rotatable disc grinding wheel 232 in contact with the tip portion of the brush 231.
The grinding with electrolytic inprocess dressing further comprises a lead wire 237 connected to a cathode electrode (-) of the supply source 230, a counter electrode 233 connected to the lead wire 237 at a certain distance to a grinding surface of the grinding wheel 232, and a nozzle 234 arranged between the grinding wheel 232 and the negative electrode 233 and for spraying weakly conductive coolant, thereby obtaining inprocess dressing effect resulting in a dressing by the grinding wheel 232 during machining of silicon ingot (work) 235.
In the above method, the position of the electrode 233 is always fixed with respect to the shaft of the grinding wheel 232 to hold a slight gap (0.1.about.0.2 m/m) between the electrode 233 and the grinding surface of the wheel 232 constant. The grinding is performed at the position that the electrode 233 and the work 235 loaded in a chuck which is held in a turning center 238, are not subjected to an interference effect with each other. Reference numeral 239 is a supply nozzle for machining coolant.
In case of performing the machining, such as roughing, polishing, centering and edging which are required to the machining of optical components in the above conventional machining method, respective machining steps must be performed by respective units, for example, even in roughing polish steps, respective machining units are necessary for respective steps, such as tentering, rounding, chamfering, fine lapping and polishing, so that production efficiency becomes very poor. Moreover, in the optical components having a plurality of diameters for each diameter the, collet chuck holding the optical components must be interchanged, so that machining process becomes very inefficient and thus it takes too much time to carry out the machining.
Moreover, in grinding with electrolytic inprocess dressing to obtain the inprocess dressing, the work and the electrode must be arranged in such a manner that these work and electrode are not subjected to a interference effect with each other.